Alloy for use as stents

ABSTRACT

Alloys for use as stents which consist essentially of niobium (Nb), tantalum (Ta) and zirconium (Zr).

BACKGROUND OF THE INVENTION

[0001] The invention concerns alloys composed essentially of niobium (Nb), tantalum (Ta) and zirconium (Zr) for use as stents, as well as stents made of these alloys.

[0002] Stents are well known in themselves and are described, for example, in U.S. Pat. No. 5,628,787, U.S. Pat. No. 5,630,840, and EP-A-0 873 734. Alloys that have been proposed for stents include not only special steels, but also nickel and tantalum alloys and niobium-zirconium alloys, in which the Nb content is greater than 90% and preferably greater than 95% or 98% (WO 02/43,787).

SUMMARY AND DESCRIPTION OF THE INVENTION

[0003] The object of the present invention is to provide alloys that satisfy stringent requirements with respect to biocompatibility, contain no known allergens, have good mechanical properties, are visible in radiographs, and can be identified in nuclear spin tomography.

[0004] Surprisingly, it was found that stents made of the alloys of Nb, Ta, and Zr that are described below have the following combination of properties: good biocompatibility with very good mechanical properties, x-ray opacity, and identifiability in nuclear spin tomograms due to their magnetic properties. Alloy components that could cause problems, such as nickel, are absent, the x-ray opacity is not overly great as in the case of alloys with a very high Ta content, and identifiability with the nuclear spin method is an important advantage in view of the increasingly widespread use of this method.

[0005] The niobium content is greater than 50% and preferably greater than 80%, and the rest of the alloy consists essentially of Ta and Zr. The Zr content is less than 5%, and the zirconium content is generally less than the tantalum content. In addition, the niobium content is preferably less than 90%.

[0006] Preferred alloys have the following contents: 1. 50-98.9% Nb, 0.5-5% Zr, 0.6-49.5% Ta; 2. 90-98.9% Nb, 0.5-5% Zr, 0.6-9.5% Ta; 3. 80-97% Nb,   2-5% Zr,   1-18% Ta; 4. 80-90% Nb, 0.5-5% Zr,   5-19.5% Ta.

[0007] Alloys with a niobium content of 80-90% are especially preferred. The increase in x-ray opacity and improvement of the mechanical properties work out favorably here—with the possibility of reducing the cross section of the mesh links of the stent.

[0008] Alloys that contain more tantalum than zirconium are also preferred embodiments of the invention.

[0009] The following are examples of especially preferred alloys: 5. 90% Nb, 1% Zr,  9% Ta; 6. 85% Nb, 1% Zr, 14% Ta.

[0010] The invention also concerns stents made of the alloys described above, especially stents in which the mesh links have a relatively small cross section.

[0011] The alloys and stents made of the alloys are produced by common methods with which experts are familiar.

[0012] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described therein. 

We claim:
 1. An alloy for use as stents, which is composed essentially of: 50-98.9% Nb; 0.5-5% Zr; and 0.6-49.5% tantalum.
 2. An alloy in accordance with claim 1, which is composed essentially of: 90-98.9% Nb; 0.5-5% Zr; and 0.6-9.5% Ta.
 3. An alloy in accordance with claim 1, which is composed essentially of: 80-97% Nb; 2-5% Zr; and 1-18% Ta.
 4. An alloy in accordance with claim 1, which is composed essentially of: 80-90% Nb; 0.5-5% Zr; and 5-19.5% Ta.
 5. An alloy in accordance claim 1, wherein the alloy contains more tantalum than zirconium.
 6. A stent made of an alloy composed essentially of: 50-98.9% Nb; 0.5-5% Zr; and 0.6-49.5% tantalum.
 7. A stent in accordance with claim 6, wherein the alloy which is composed essentially of: 90-98.9% Nb; 0.5-5% Zr; and 0.6-9.5% Ta.
 8. A stent in accordance with claim 6, which is composed essentially of: 80-97% Nb; 2-5% Zr; and 1-18% Ta.
 9. A stent in accordance with claim 6, which is composed essentially of: 80-90% Nb; 0.5-5% Zr; and 5-19.5% Ta.
 10. A stent in accordance with claim 6, wherein the alloy contains more tantalum than zirconium. 